1. Field of the Invention
The present invention relates to an arrangement for controlling the bus access of a plurality of devices sharing one bus in a network with at least one optical mixer constructed as a passive bus system, particularly for multi-computer systems. The devices employing the bus can be subscribers exchanging information among each other, such as individual computers of a multi-computer system.
2. The Prior Art
In passive bus systems, no preconditions are undertaken within the bus in order to permit communication among the connected devices. The connected devices may be, for example, individual computers of a multi-computer system, and no attempt is made to give any of the connected devices special priorities. Each station is of equal priority. When requests for communications simultaneously occur from several stations, measures must be taken to insure that only one station can access the bus, since with simultaneous transmission, super positon of simultaneous transmissions causes the data transfer to be falsified.
Various procedures have been applied in known bus systems, in which the access to the bus are decentrally sequenced by the individual stations. The best known access method which is also employable for optical couplers is the CSMA/CD method (Carrier Sense Multiple Access with Collision Detection). This method is carried on completely decentrally with a passive bus system.